Easy cut suspension grid

ABSTRACT

A grid runner for a suspended ceiling having a lower flange extending generally horizontally, a web extending upwardly from the flange, and walls forming a hollow reinforcing bulb at the upper end of the web, the web lying generally in an imaginary vertical plane, a portion of the walls forming the bulb being disposed on and laterally spaced from the imaginary vertical plane, a wall area of the bulb on an upper side of the bulb bridging the space between the bulb walls on opposite sides of the imaginary plane, the bulb having lower wall portions forming its base and configured such that the bulb will readily collapse at the base when a lateral shear force is applied to the bulb walls by a hand-operated snips whereby the force to manually field cut the tee is reduced.

BACKGROUND OF THE INVENTION

The invention pertains to suspended ceiling grid and, in particular, toa grid runner construction that eases the task of its installation.

PRIOR ART

Suspended ceiling grid typically is in the form of metal runners havingan inverted tee cross-section. Ceiling grid is erected on site, thereordinarily being no practical or cost-effective way to prefabricate aninstallation or even a part of an installation. Moreover, it is obviousthat the installation work cannot be done on the actual floor surface orby an installer standing directly on the floor. Rather, a technician orinstaller works off a rolling scaffold or other elevating appliance. Inthis situation, there is typically no convenient workbench or like tableto support the grid elements while length measurements are being madeand transferred to a grid tee and while a grid tee is actually being cutto the proper length. It is axiomatic that time is money and the quickerand easier a piece of grid tee can be grasped, marked for cutting, cutand installed, the more profitable a job can be. Currently, despite theproliferation of power tools, including portable power tools, theindustry largely relies on manual cutting devices in the form of snips,sometimes referred to as aviation snips. Repetitive manual cutting oftees in the customary manner can lead to fatigue in the installer's handand a consequent loss of productivity. The foregoing illustrates that agrid tee that does not sacrifice performance but is easier to manuallycut than that presently available, would be an advance in the art.

SUMMARY OF THE INVENTION

The invention provides a grid tee that can be manually cut with reducedeffort and thereby makes its installation easier, resulting in thetechnician or installer experiencing less fatigue and, potentially,greater productivity.

More specifically, the invention brings the insight that a major sourceof resistance of a grid tee to being cut is the compressive strength ofthe typical hollow reinforcing bulb formed at the upper part of the tee.With still greater insight, the invention recognizes that the grippingforce required of a technician using the usual pair of snips is relatedto the compression strength of the bulb structure, as distinguished fromthe compressive strength of the bulb material per se, at the pointfurthest from the pin joint of the pair of pivoted blades in the snips.The base area of the bulb is the part of the tee encountered by theblades that is furthest from the pivot pin of the hand snips when theinitial effort is made to cut the top of the tee. This area, therefore,has a relatively large lever arm of resistance measured from the pivotpoint of the snips and thus can create a high resistance to the closingsnip's blades and prevent the metal stock of the tee to be shearedeasily.

The invention reduces the problem of high forces that are otherwiseordinarily necessary to manually cut a tee. This is accomplishedaccording to the invention by incorporating certain structure/geometryin the base of the bulb, the location of the tee structure that is thegreatest distance from the pivot pin of the snips when the bulb is beingcut. These structures are used to more readily initiate buckling orcrushing of the bulb base area when it is subjected to the lateralcompressive forces being applied by the snip blades. Once the bulb hasbeen crushed and flattened by the blades, the blades can shear the bulbstock more readily, especially if the snips are urged forwardly into theactual cutting zone, thereby keeping the leverage of the handles high.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an end view of a conventional style grid tee;

FIG. 2 is an end view of a first embodiment of a grid tee according tothe invention;

FIG. 3 is an end view of a second embodiment of a grid tee according tothe invention; and

FIG. 4 is an end view of a third embodiment of a grid tee according tothe invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 illustrates a traditional prior art grid tee or runner 10 inprofile or cross-section. This prior art style grid tee 10 and the gridtees described hereinbelow incorporating the present invention areelongated shafts assembled into a rectangular gridwork typicallysuspended from overhead or superstructure and on which tiles are mountedto construct a suspended ceiling. The gridwork, typically, comprisesmain tees and intersecting cross tees; grid modules are typically 2 footby 2 foot or 2 foot by 4 foot or metric equivalent. The main tees areprovided with regularly spaced slots in their mid-section or web thataccept connectors provided on the ends of cross tees as is customary inthe industry. Main tees are connected end-to-end with suitable endconnectors, known in the art, to span the ceiling area. The main andcross tees can have the same cross section or profile or the cross teescan have a lighter duty section such as having a reduced height.

The grid tee 10 of FIG. 1 and the others disclosed hereinafter areformed of sheet metal, usually steel, by known roll forming processes.The grid tee or runner 10 has a lower horizontal flange 11, a verticalweb 12, and a hollow reinforcing bulb 13 formed of one metal strip. Thetee 10 includes a sheet metal cap strip 14 that forms a lower normallyvisible face 16. The cap strip 14 is captured on the flange 11 bymarginal hems 17 folded over the backside of the flange. Commonly,acoustic, fire-resistant tile is laid between the tees forming thesuspended grid to rest on the flanges 11, thereby making up a ceiling.

Referring now to FIG. 2, there is shown a grid tee 21 embodying one formof the present invention. For the sake of simplicity, parts of the tee21 of FIG. 2, as well as those to be described in connection with FIGS.3 and 4, having the same construction and/or function as thecorresponding parts of the tee 10 of FIG. 1, are designated with thesame numerals.

The grid tee 21 includes an upper hollow reinforcing bulb 22. The bulbhas an upper generally horizontal wall 23 joined at each of its edges byfolded corners to respective generally vertical flat sidewalls 24, 25.The sidewalls 24, 25 extend to folded corners where they are joined togenerally horizontal walls 26, 27. In turn, the horizontal walls 26, 27extend to corner folds where they are joined to respective layers of avertical web 12. The vertical bulb wall 24, shown on the left in FIG. 2,is somewhat shorter than the right vertical bulb wall 25 and thehorizontal bulb walls 26, 27 lie on different horizontal planes.Specifically, the left-hand generally horizontal bulb wall 26 is at anelevation above that of the right-hand generally horizontal bulb wall27.

In the installation of a ceiling grid, standard lengths of grid tees arejoined together. Usually, some of the tees have to be cut to fit a gridto the boundaries of a ceiling area and around structures or accessoriesthat penetrate the plane of the ceiling. Commonly, grid tees are cut tolength in the field, based on actual field measurements. This practicetypically involves the use of so-called “aviation snips” or tin snipsthat are hand-held and hand-powered. Presumably, this is the tool ofchoice of installers because it is lightweight, durable, and enables theinstaller to use it for “fancy” cuts at special or odd junctures such asinvolving angles other than a perpendicular cut and for similar duty. Adifficulty lies in cutting a conventional prior art tee 10 in the areaof the bulb 13. Several factors contribute to the difficulty. It is tobe realized that the snips cut by shearing action between its opposedblades. However, before effective shearing action by and at the bladescan occur, the grid tee bulb 13 must first be crushed to bring the wallsof the bulb on opposite sides of the central imaginary plane of the webtogether.

Unlike the hollow reinforcing bulb 13 of the prior art grid tee 10 whichis symmetrical about a central imaginary vertical plane bisecting thedouble layer web 12, the tee 21 shown in FIG. 2 has an upper hollowreinforcing bulb 22 that is asymmetrical about the imaginary verticalplane bisecting its double layer web 12.

To embrace the width of a hollow bulb requires that the blades and,therefore, the handles of a snips be considerably open thereby making itdifficult to get a good, strong finger grip on the handles. The lowerpart or bottom part of the bulb, that is the wide bulb part furthestfrom the top of the bulb, can ordinarily present the greatest difficultyby resisting crushing forces, because it has the greatest leverage,measured by its distance from the pivot of the blades, as compared toother parts of the bulb.

The invention comprehends the provision of a deliberate eccentricity ofthe structure at the base of the bulb that promotes or encouragesbuckling in this area when a lateral compressive force is applied to thesides of the bulb by the blades of a snips. This eccentricity isaccomplished in the embodiment of FIG. 2 by creating the structure atthe base of the bulb 22 represented by the horizontal walls 26, 27 wherethese walls cannot strongly support one another when they are subjectedto lateral compressive forces. The walls 26, 27 are unable to laterallysupport one another because they are misaligned so as to deliberately besituated in different planes, the plane of the wall on the left beinghigher than the plane of the wall on the right. This difference inheight or degree of eccentricity is preferably greater than thethickness of the walls 26, 27. By way of contrast, inspection of FIG. 1reveals that the lower wall portions of the reinforcing bulb 13 of theconventional prior art grid tee are in alignment. That is, these lowerwalls of the prior art tee bulb 13 converge at the web 12 at the samevertical location and, further, lie in a common imaginary horizontalplane.

FIG. 3 illustrates a grid tee 31 made according to a second embodimentof the invention, where again, a lower part of a reinforcing bulb 32 isdeliberately made incapable of strongly resisting lateral compressiveloads imposed by the blades of a snips. In this embodiment, the lowerpart of the bulb 32 is represented by left and right lower or base walls33, 34, each converging with a respective layer of a web 12 at differentelevations and with vertical bulb sidewalls 38, 39 at similarlydifferent locations. FIG. 3 reveals that the walls 33, 34 cannot supportone another against a lateral compressive load since they are misalignedwhere they intersect with the web 12. Moreover, the walls 33, 34 do notlie in horizontal planes which would otherwise present them in a more orless stable condition to resist lateral forces. The inclination of thesewalls 33, 34 from a horizontal plane encourages them to fold upwardlyand thereby collapse when subjected to lateral compressive forces.Additionally, the bulb 32 has an inclined or slanted top wall 36 whichcan be more prone than a horizontal wall to collapse by folding inwardlyat an acute corner 37 when squeezed between the blades of a snips.

FIG. 4 illustrates a grid tee 41 of still another embodiment of theinvention. In this embodiment, both lower wall portions 42 and 43, andupper wall 44 of a hollow reinforcing bulb 45 are constructed to moreeasily buckle under the lateral compressive forces developed by theblades of a snips being used to cut the tee as compared to generallyflat horizontal walls. The lower wall portions 42, 43 of the bulb arearranged with two features that can be operative to produce a structureprone to collapse or buckle under lateral applied forces. The lower wallportions 42, 43 are oriented, in an overall sense, at an inclined angleof, for example, about 45 degrees. Still further, the walls 42, 43 arecreased or folded inwardly or concavely at their mid-points 46 makingthem weak against lateral forces and any force along an imaginary planebetween their points of convergence with a bulb sidewall 47 and avertical web 12. It will be seen that the crease 46 in these lower wallportions 42, 43 is at a depth, i.e. the wall portion deviates from aflat plane, that is preferably greater than the gauge thickness of thesheet material from which the tee 41 is made. The upper wall 44 of thetee bulb 45 is also arranged to collapse under lateral loading whencompressed by a snips. In this arrangement on each side of an imaginarymid-plane vertically through the web 12 the upper wall 44 is formed witha crease 48 that is concave with reference to the bulb exterior. Likethe crease 46 in the lower walls 42, 43, this formation promotesbuckling action in the upper bulb wall 44.

A grid runner for a suspended ceiling having a lower flange extendinggenerally horizontally, a web extending upwardly from the flange, andwalls forming a hollow reinforcing bulb at the upper end of the web, theweb lying generally in an imaginary vertical plane, a portion of thewalls forming the bulb being disposed on and laterally spaced from theimaginary vertical plane, a wall area of the bulb on an upper side ofthe bulb bridging the space between the bulb walls on opposite sides ofthe imaginary plane, the bulb having lower wall portions forming itsbase and configured such that the bulb will readily collapse at the basewhen a lateral shear force is applied to the bulb walls by ahand-operated snips whereby the force to manually field cut the tee isreduced.

The vertical flat sides of the reinforcing bulbs 22, 32, and 45, arepreferably relatively long in vertical extent, being at least as long asthe respective bulb is wide, to impart to the respective tee a highvertical beam strength and high resistance to lateral bending. While theillustrated tees are shown as roll-formed sheet metal products, it iscontemplated that the invention can be utilized in extruded tees and thetees can be made of aluminum or suitable rigid plastic.

While the invention has been shown and described with respect toparticular embodiments thereof, this is for the purpose of illustrationrather than limitation, and other variations and modifications of thespecific embodiments herein shown and described will be apparent tothose skilled in the art all within the intended spirit and scope of theinvention. Accordingly, the patent is not to be limited in scope andeffect to the specific embodiments herein shown and described nor in anyother way that is inconsistent with the extent to which the progress inthe art has been advanced by the invention.

1. A grid runner for a suspended ceiling having a lower flange extendinggenerally horizontally, a web extending upwardly from the flange, andwalls forming a hollow reinforcing bulb at the upper end of the web, theweb lying generally in an imaginary vertical plane, a portion of thewalls forming the bulb being disposed on and laterally spaced from theimaginary vertical plane, a wall area of the bulb on an upper side ofthe bulb bridging the space between the bulb walls on opposite sides ofthe imaginary plane, the bulb having lower wall portions forming itsbase and configured such that the bulb will readily collapse at the basewhen a lateral shear force is applied to the bulb walls by ahand-operated snips whereby the force to manually field cut the tee isreduced.
 2. A grid tee as set forth in claim 1, wherein said tee isformed of sheet metal stock that is roll-formed.
 3. A grid tee as setforth in claim 1, wherein said bulb includes vertical walls that aregenerally flat.
 4. A grid tee as set forth in claim 3, wherein saidvertical walls are greater in vertical length than the horizontal widthof the bulb.
 5. A grid tee as set forth in claim 1, wherein the upperportion of the bulb comprises a generally horizontal wall.
 6. A grid teeas set forth in claim 1, wherein said grid tee includes an upper wallthat is slanted from the horizontal.
 7. A grid tee as set forth in claim1, wherein said tee includes an upper wall that is peaked at saidimaginary mid-plane of said web.
 8. A grid tee as set forth in claim 7,wherein said peaked upper wall is concavely creased on opposite sides ofsaid imaginary mid-plane.
 9. A grid tee as set forth in claim 1, whereinsaid reinforcing bulb has lower wall portions on opposite sides of saidimaginary plane, said lower walls being creased concavely to provide astructure which is readily collapsible under lateral loads.
 10. A gridtee as set forth in claim 9, wherein said lower wall portions merge withsidewall portions of said bulb at one elevation, and merge with the webof the grid tee at an elevation below said first-mentioned elevation.11. A grid tee as set forth in claim 1, wherein said lower wall portionslie on each side of said imaginary vertical plane, the lower wallportion area on one side of the imaginary plane being generally higherin elevation than the lower wall portion area on the other side of theimaginary plane whereby said lower wall portion areas are verticallyoffset from one another and the consequent eccentricity of these lowerwall portion areas prevents them from strongly supporting each otheragainst lateral compressive forces developed by the blades of the snips.